Commit d0898152 authored by Daniel Leung's avatar Daniel Leung Committed by Benjamin Cabé
Browse files

soc: intel_adsp/ace: use custom arch_spin_relax() 

Intel Audio DSP ACE needs to use arch_spin_relax() to give
the bus more time to propagate the RCW transactions among
CPUs, and to avoid sending too many requests to the bus
after failing to lock spinlocks. However, the number of
NOPs results in a very big arch_spin_relax() that spans
multiple instruction cache lines, and requires evicting
them just for NOPs.  With 5 CPUs, it can span 6 cache
lines (if using nop.n instead of nop). That's a waste of
space and cache. So instead, we do a tight loop instead.
Since the SoC supports zero-overhead loops, this should
have minimal performance impact.

Signed-off-by: default avatarDaniel Leung <daniel.leung@intel.com>
parent 58b035b8

soc/intel/intel_adsp/ace/CMakeLists.txt

+4 −0
Changes for soc/intel/intel_adsp/ace/CMakeLists.txt: 4 added lines, 0 removed lines.
Original line number Diff line number Diff line
@@ -18,6 +18,10 @@ zephyr_include_directories(include) 
zephyr_include_directories(include/${CONFIG_SOC})

zephyr_library_sources_ifdef(CONFIG_SOC_INTEL_COMM_WIDGET comm_widget.c)

zephyr_library_sources_ifdef(CONFIG_SOC_INTEL_COMM_WIDGET comm_widget_messages.c)

zephyr_library_sources_ifdef(

  CONFIG_SOC_SERIES_INTEL_ADSP_ACE_CUSTOM_MORE_SPIN_RELAX_NOPS

  spin_relax.c

)



if (CONFIG_XTENSA_MMU)

  zephyr_library_sources_ifdef(CONFIG_SOC_INTEL_ACE30 mmu_ace30.c)

soc/intel/intel_adsp/ace/Kconfig

+21 −0
Changes for soc/intel/intel_adsp/ace/Kconfig: 21 added lines, 0 removed lines.
Original line number Diff line number Diff line
@@ -31,3 +31,24 @@ config SRAM_RETENTION_MODE 
	  When this option is enabled, the SRAM retention mode will be

	  activated during the firmware boot-up process. If disabled,

	  the retention mode will not be activated.



config SOC_SERIES_INTEL_ADSP_ACE_CUSTOM_MORE_SPIN_RELAX_NOPS

	bool "Use Intel Audio DSP specific arch_spin_relax() with more NOPs"

	depends on !XTENSA_MORE_SPIN_RELAX_NOPS

	default y if SMP && MP_MAX_NUM_CPUS > 1

	help

	  Add some NOPs after failure to lock a spinlock. This gives

	  the bus extra time to synchronize the RCW transaction

	  among CPUs.



config SOC_SERIES_INTEL_ADSP_ACE_NUM_SPIN_RELAX_NOPS

	int "Number of NOPs to be used in Intel Audio DSP specific arch_spin_relax()"

	depends on SOC_SERIES_INTEL_ADSP_ACE_CUSTOM_MORE_SPIN_RELAX_NOPS

	default 32 if MP_MAX_NUM_CPUS = 1

	default 64 if MP_MAX_NUM_CPUS = 2

	default 96 if MP_MAX_NUM_CPUS = 3

	default 128 if MP_MAX_NUM_CPUS = 4

	default 160 if MP_MAX_NUM_CPUS = 5

	help

	  Specify the number of NOPs in Intel Audio DSP specific

	  arch_spin_relax().

soc/intel/intel_adsp/ace/Kconfig.defconfig.series

+0 −14
Changes for soc/intel/intel_adsp/ace/Kconfig.defconfig.series: 0 added lines, 14 removed lines.
Original line number Diff line number Diff line
@@ -57,20 +57,6 @@ config LOG_BACKEND_ADSP 


endif # LOG



config XTENSA_MORE_SPIN_RELAX_NOPS

	default y if SMP && MP_MAX_NUM_CPUS > 1



if XTENSA_MORE_SPIN_RELAX_NOPS



config XTENSA_NUM_SPIN_RELAX_NOPS

	default 32 if MP_MAX_NUM_CPUS = 1

	default 64 if MP_MAX_NUM_CPUS = 2

	default 96 if MP_MAX_NUM_CPUS = 3

	default 128 if MP_MAX_NUM_CPUS = 4

	default 160 if MP_MAX_NUM_CPUS = 5



endif # XTENSA_MORE_SPIN_RELAX_NOPS



if KERNEL_VM_SUPPORT



config KERNEL_VM_SIZE

soc/intel/intel_adsp/ace/spin_relax.c

0 → 100644
+33 −0
Changes for soc/intel/intel_adsp/ace/spin_relax.c: 33 added lines, 0 removed lines.
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2025 Intel Corporation

 *

 * SPDX-License-Identifier: Apache-2.0

 */



#include <stdint.h>



#include <zephyr/toolchain.h>

#include <zephyr/sys/util_macro.h>



#ifdef CONFIG_SOC_SERIES_INTEL_ADSP_ACE_NUM_SPIN_RELAX_NOPS

void arch_spin_relax(void)

{

	register uint32_t remaining = CONFIG_SOC_SERIES_INTEL_ADSP_ACE_NUM_SPIN_RELAX_NOPS;



	while (remaining > 0) {

#if (CONFIG_SOC_SERIES_INTEL_ADSP_ACE_NUM_SPIN_RELAX_NOPS % 4) == 0

		remaining -= 4;



		/*

		 * Note the xcc/xt-clang likes to "truncate"

		 * continuous NOPs to max 4 NOPs. So this is

		 * the most we can do in one loop.

		 */

		__asm__("nop.n; nop.n; nop.n; nop.n;");

#else

		remaining--;

		__asm__("nop.n");

#endif

	}

}

#endif /* CONFIG_SOC_SERIES_INTEL_ADSP_ACE_NUM_SPIN_RELAX_NOPS */

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